The present invention relates to a method and apparatus for stamping and cutting plastic parts.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Multilayered plastic parts find application in the automobile industry for example, and typically include a plastic carrier which is covered by a layer of semi-hardened polyurethane foam which in turn is covered on the visible side by a decorative surface layer of thin plastic material. The various layers are applied successively during production of such multilayered plastic parts. Multilayered plastic parts are semi-finished products which often are required to have cut edges and openings. In order to obtain such a cut edge, it is customary to finish them by means of a stamping operation or milling operation or a combination of both methods.
The various operating steps for cutting of the semi-finished product are normally executed in succession in different work stations. Using different work stations is needed because of the complex geometric shapes of the parts to be machined, rendering the application of a single cutting operation impossible. As a result, the stamping operation is normally followed by a flexible cutting process to finish the semi-finished product and to provide the multilayered plastic part with openings or recesses.
Conceivably, a first stamping step may be followed by a second stamping step, although normally the second operating step involves milling to work on regions which cannot be stamped for geometric reasons. Executing a milling step after the stamping operation involves the use of a hydraulic machine with a milling cell in which the previously stamped plastic part is placed and worked on. Thus, it is required to remove the plastic part from a first stamping station and then place it into the milling cell. This causes an adding up of various tolerances which result in an overall tolerance that in many cases is unacceptable. A particular problem is the implementation of the second cut with tolerance with respect to the first cut.
To address the problem of adding up tolerances, it is proposed to directly finish the previously stamped plastic part in the stamping press by attaching a milling robot directly onto the stamping tool. The milling robot then immediately mills those regions that cannot be stamped during the initial stamping operation. This causes however shavings that accumulate, thereby rendering a precision stamping of a subsequent part in the same stamping press impossible.
It would therefore be desirable and advantageous to address this problem and to obviate other prior art shortcomings and to realize consistently desired tolerances, even when complex geometries are involved.